Filter elements of various types are utilized to filter media or fluids flowing through the fluid lines of a fluid handling system. The fluid handling system may be provided for any number of processes involving one or more liquid-phase sample preparation, transfer and/or analytical tasks. A few examples include high-throughput liquid sample assaying, dissolution testing, and various types of chromatography, spectroscopy, and spectrometry. Filter elements are often installed in-line in such systems. For this purpose, each filter element may be individually housed in some type of filter unit equipped with fittings adapted for coupling to and decoupling from the fluid lines in which the fluid flows. An example of a filter unit is described in U.S. Pat. No. 6,490,782, which is incorporated by reference herein in its entirety. This type of filter unit has a polymeric housing that encloses a standard disk-shaped filter element and provides an inlet and outlet in the form of Luer-type male and female fittings. In any filter unit, the filter element has a limited useful life. That is, after a period of service, degradation, clogging and other conditions reduce the effectiveness of the filter element enough that the filter element must be replaced. The down-time and labor attending the replacement of filter elements have led to development of automated filter changing apparatus such as disclosed in the above-referenced U.S. Pat. No. 6,490,782.
The known filter changing apparatus of U.S. Pat. No. 6,490,782 is capable of coupling multiple Luer-type filter units to a corresponding number of individual fluid lines of a multi-channel fluid handling system, and changing out the multiple filter units with new filter units in a single filter-changing process. However, because the individual filter units have complex geometries and must be individually manipulated, moved and coupled to fluid lines by the filter changing apparatus, the mechanisms and components of the filter changing apparatus are relatively complex and the filter changing apparatus is relatively bulky and occupies significant bench-top space. Moreover, the filter units are typically provided in the form of vertical stacks in which the inlet of each filter unit is initially connected to the outlet of an adjacent filter unit. These stacks are loaded into the known filter changing apparatus, which is configured to disconnect the bottom-most filter unit from the stack and transport it to a fluid line for in-line coupling. The filter units are lengthy from inlet to outlet. Thus, a stack of just a few filter units has a significant height and, when loaded onto the known filter changing apparatus, occupies significant vertical space. To increase the amount of filter units available for replacement, the known filter changing apparatus provides a carousel on which multiple stacks of filter units may be loaded. The carousel, however, increases the footprint of the filter changing apparatus and adds to its complexity.
In view of the foregoing, there is a need for providing improved units for housing filter elements and apparatus and methods for replacing filter elements in the context of in-line filtering systems.